Energy consumption has increased by 50% over the last 25 years with 80% of the world's power still generated by fossil fuels. Clean, renewable alternative energy sources are needed to meet increasing energy consumption. Photovoltaic solar technology is viewed as one possible solution, but to meet the increasing demands, dramatic improvements are needed in solar conversion efficiency and cost/complexity reduction. Currently available mass produced low cost solar panels are at best about 10% efficient, with an upper theoretical limit of about 30% efficiency.
An alternative approach to photovoltaic technology is the fabrication of an array of optical antennas with rectifier elements located at the outputs of the optical antennas. These antennas elements are known as “rectennas”. There is no fundamental efficiency limit to rectenna arrays and conversion efficiencies of >85% have been achieved at microwave frequencies as a method of wireless power transmission. The main reason that solar rectenna technology has not achieved wide acceptance is the difficulty of fabricating efficient rectifier elements at optical frequencies that work at the low fields present at each rectenna element.